This invention relates to an improved roofing nail, specifically a self-supporting roofing nail for use in fastening roofing felt to a wooden roof substructure.
Roofing felt, or tar paper as it is commonly called, is a material widely used in the construction industry to weather-proof the roof of a building. Typically, a wooden substructure is constructed to form the roof line of a building. The substructure includes a covering of sheets of plywood or similar wooden material over the roof trusses. Roofing felt is then applied over the wooden substructure in a layered fashion from the bottom of the roof to the top. Finally, shingles or some similar material is applied over the roofing felt to complete the roofing process. A roof constructed of roofing felt and shingles provides a very effective weather resistant covering to a building.
Roofing felt is not necessarily a strong material. The advantage of roofing felt is its ability to resist moisture penetration. Thus, it is used as a moisture barrier between the wooden substructure of the roof and the shingles. It will fail quite easily under shear or tension stresses applied to it. Consequently, when applying roofing felt to a roof the installer must use a special type of nail which will have a relatively large bearing area over the roofing felt. A common nail or even a roofing nail has a head which is too small to prevent the nail head from penetrating the felt. A large bearing area prevents the nail head from penetrating the felt and compromising the moisture resistant characteristic of the roofing felt.
The type of nail which is most commonly used in applying roofing felt is a cap nail. A cap nail is typically a two-piece nail. The fist component is a straight shanked roofing nail with a formed flat head perpendicular to the shank of the nail. The second component is the cap which is essentially a flat plate substantially larger than the head of the nail. The cap has a hole in the middle through which the shank of the nail is disposed and the cap, usually made of metal, is wedged on the nails adjacent the head of the nail.
Traditionally, when applying the roofing felt to the wooden roof substructure, the carpenter inserts the nails in the roof by holding the nail with his fingers and tapping the nail until it becomes seated, and then hitting the nail hard to force it into the roof. Generally, the carpenter tries to release the nail just before he hits it with a hammer so that his fingers do not get struck by the hammer.
There are several disadvantages to using this type of roofing nail. First, because of the large cap wedged adjacent the nail head, a carpenter must reach under the cap with his fingers and hold the nail while seating it with a hammer. Typical roofing nails are one inch or less in length. Thus, using fingers to hold the nail shank under the cap on such a short nail becomes relatively difficult for the carpenter. The carpenter also has difficulty in removing his fingers from the nail in time to avoid being caught by the hammer and cap when the nail is being driven thereby risking injury to fingers. Second, if a carpenter removes his fingers too soon and the nail tips over, the nail is poorly driven and must be removed and discarded, therefore wasting time and materials. This occurs on as many as 25% of the roofing nails installed. Third, when a nail is driven poorly, the defect may be concealed by the cap. Thus, a poorly driven nail may be left in the roof and not properly performing the function for which it was designed. Since a defectively driven nail cannot be identified by visual inspection, many of these nails stay on the roof only partially holding the roofing felt. Such a condition can cause roof felt failure by being blown off by wind.
In view of the above problems as well as other considerations, it is believed that an improved roofing nail should provide at least some of the following advantages: The ability to be easily seated and driven on the roofing felt without endangering injury to the carpenter's fingers, a low rate of improper installation, and the ability to be easily inspected for proper installation. Therefore, the purpose of the present invention is to improve the design and construction of a roofing nail to incorporate these advantages.